Metal refining process



Patented Feb. 22, 1944 2,342,102 I METAL REFINING PnocEss Norval D. Clare, Niagara Falls, N. Y., assignorto- E. I. du Pont de Nemonrs & Company, Wilmington, Del., a corporation of Delaware No Drawing. Application October 20, 1941, Serial No. 415,771

9 Claims.

This invention relates to refining metals and more particularly to removal of phosphorus from metals.

Phosphorus is a deleteriousconstituent when phorus in'the production of cast iron, steel and ferro alloys is controlled oxidation, preferably in the presence of basic slag. In the practice of this method, however, desirable constituents of the melt which are easily oxidized (for example carbon, manganese, and chromium) are frequently removed, either in part or entirely, and this makes for both monetary loss and for uncertainty in calculating the final composition of the steel or other alloy. I

An object of the present invention is a new and improved method of refining metals to partially or completely remove phosphorus. Another object is to so removephosphorus from metals without substantially decreasing the concentration of valuable, oxidizable constituents such as manganese, carbon, or chromium in metals so refined. Another object is the production of copper and copper alloys substantially free from phosphorus. Further objects will be apparent from the ensuing description of my invention.

I have discovered that by treating phosphoruscontaining metals in a molten state, with an oxide of an alkali metal, the phosphorus may be wholly or completely removed without loss of such other constituents as are ordinarily lost when the melt is given an oxidizing treatment. For example, by the addition of sodium monoxide (NaaO) or potassium oxide (K) to a manganese steel containing phosphorus, I may substantially completely remove the phosphorus or reduce it to a very small concentration without substantial loss of manganese or carbon. ,M process also results in removal of sulfur, if any is present in the metal treated. Any oxide or peroxide of n alkali metal, or mixtures thereof, are suitable for my process, but I prefer to utilize an alkali metal monoxide, e. g., sodium monoxide.

I am aware that it has been proposed heretofore to refine molten metals by adding sodium carbonate, for removal of sulfur. I have found,

however, that alkali-oxide is much more active than the corresponding carbonate in removing phosphorus. For example, I found that when separate melts of phosphorus-containing steel were treated separately with chemically equivalent amounts of sodium carbonate and sodium monoxide, the amount of phosphorus remaining in the steel after treatment with the monoxide was half of that remaining after treatment with the carbonate. From these results it is apparent that the oxide treatment permits a greater removal of phosphorus with a'smaller weight of refining agent, as compared with carbonate treatment.

My invention may be practiced in a number of ways obvious to those skilled in the art. The essential feature is to secure contact between the alkali metal oxide and the metal treated. I prefer not to add the oxide to any slag that may be present since oxides of sodium and potassium incorporate readily into such slags and are thereby diluted sothat' their unique properties are either attenuated or lost. The alkali oxide may be added directly to the metal, either in one batch or by successive additions; or the-metal may be poured onto the oxide. The alkali oxide may be floated in a stream of gas and blown over or through the metal. The alkali oxide may be added enclosed in metal containers of a sort that will melt when in contact with the metal being treated, or such containers may bethrust under the surface of the molten metal to be treated. The oxides may conveniently be preformed into briquettes or cast blocks in a variety of ways to provide a form convenient for addition to a metal melt. Thus, taking the oxides of sodium as an example, sodium monoxide and sodium peroxide -may be fused together and cast in molds. The

alkali metal oxides may be briquetted by mixing them in a finely divided state with a small amount, such as 1 to 10%, of a fusible salt, e. g.. borax or sodium nitrate, or with a. heavy metal oxide, e. g., an iron oxide, and heating the mix ture in a mold, preferably under pressure.

The amount of alkali oxide to be added will vary with the degree of purity of the metal to be treated, and the extent of refining desired. Preferably, I add, in most cases, an amount equal to l to 10 molar equivalents of the oxide for each atomic equivalent of phosphorus desired to be removed from the melt. If desired, the melt may be given two or more successive treatments with the alkali oxide, and this is generally preferable when complete removal of phosphorus is the object.

v The following examples illustrate specific methods of practicing the invention:

Example 1 To 180 pounds of molten castiron 2 pounds of sodium monoxide is added. After the reaction has ceased, a second charge of zpounds of sodium monoxide is added and when this has reacted, the metal is poured.

Example 3 Two pounds of sodium monoxide are placed in a ladle and immediately 200 pounds of molten copper containing a small residual amount of phosphorus are poured into the ladle on top'of the monoxide.

'. Example 4 Sodium monoxide is mixed with small pieces of iron in the proportion of 20 parts of iron to 80 parts of monoxide, although it, must be understood that'this proportion may be varied within wide limits. and this mixture is placed in an iron pot, covered, heated to a red heat, and cooled. There results a dense solid mass which may be broken into lumps of any desired size. This material is used in place of the more usual forms of sodium monoxide in the same manner as described in the other examples given but in proportionately larger amounts when cast iron, steel. or term alloys are to be treated.

Example 5 Sodium monoxide is placed in sealed metal containers or in containers having small vent holes to permit escape of heated air, such containers to be made of metals which can be added to the melt to be treated without ill eifect and which will melt at the temperatures concerned. A molten metal can then be treated by adding monoxide in such a container, either in the manner of examples previously given or by thrusting the container and its contents under the surface of the molten'metal to be treated.

Example 8 Sodium monoxide, in th form of a finely divided powder, can be mixed in a stream of any suitably non-reactive, or oxidizing gas, and the resultant mixture can be blown over the surface of the molten metal to be treated, or introduced under the surface and allowed to bubble up through the melt.

I claim.

l. The process for removing phosphorus from a metal, which comprises adding to said metal in the molten state a solid material made by fusing a mixture of a heavy metal oxide and an oxide of an alkali metal.

2. The process for removing phosphorus from a metal, which comprises adding to said metal in the molten state a solid material made by fusing a mixture of a heavy metal oxide and an oxide of sodium.

3. The process for removing phosphorus from a metal, which comprises adding to saidmetal in the molten state a solid material made by fusing an alkali metal monoxide with about 1 to 10% by weight of a heavy metal oxide.

4. The process for removing phosphorus from a metal, which comprises adding to said metal in the molten state a solid material made by fusing sodium monoxide with about 1 to 10% by weight of iron oxide.

5. The process for removingphosphorus from a ferrous metal, which comprises adding to said metal in-the molten state a solid material made by fusing a mixture of a heavy metal oxide and an oxide of an alkali metal.

6. ,The process for removing phosphorus from manganese-containing steel, which comprises adding to said steel in the molten state a solid material made by fusing sodium monoxide with about 1 to 10% by weight of iron oxide.

7. The process for removing phosphorus from a cupreous metal, which comprises adding to said metal in the molten state a solid material made by fusing an oxide of an alkali metal with a heavy metal oxide. 7

8. The process for removing phosphorus from copper which comprises adding to said copper in the molten state a solid material made by fusing an oxide of sodium with about 1 to 10% by weight of iron oxide.

I 9. The process for removing phosphorus from copper which comprises adding to said copper in the molten state a solid material made by fusing sodium monoxide with about 1 to 10% by weight of iron oxide.

NORVAL D. CLARE. 

